1. Field of the Invention
This invention relates to an information recording/reproducing method of effecting the recording and/or reproduction of information on a disk-like recording medium, and particularly to an information recording/reproducing method in which the recording area of a recording medium is divided into a plurality of zones in the radial direction of the recording medium and the recording/reproduction of information is effected with the rotational speed of the disk made to be different in each zone, whereby the spatial record length of a recording pit is made constant over the entire recording area.
2. Related Background Art
Information recording/reproducing methods of recording/reproducing information on a disk-like recording medium (hereinafter referred to as the disk) include a magnetic recording/reproducing method directed to a floppy disk and an optical information recording/reproducing method directed to a CD or a magneto-optical disk.
The diameter of disks used in these methods is prescribed as 5.25 or 3 inches, and the recent technical task is how densely information can be recorded on disks of such a diameter.
Various information recording/reproducing methods have heretofore been devised to solve such a task and above all, attention has been paid to a method called MCAV (modified constant angular velocity) or ZCAV (zone constant angular velocity). According to this method, the recording area on the disk is divided into a plurality of zones in the radial direction of the disk, and the recording/reproducing frequency of each zone is made higher from the inner peripheral zone toward the outer peripheral zone, thereby making the recording density on the inner and outer peripheries of the recording area constant. According to this method, as compared with the conventional method of effecting recording/reproduction with the number of revolutions and the recording/reproducing frequency kept constant, there is obtained an about 50% increase in recording capacity.
Another method to which attention has been paid is a method called MCLV (modified constant linear velocity) or ZCLV (zone constant linear velocity) in which the recording area on the disk is divided into a plurality of zones in the radial direction of the disk and the number of revolutions of the disk in the respective zones is made lower from the inner peripheral zone toward the outer peripheral zone, thereby making the recording density on the inner and outer peripheries of the recording area constant. Again by this method, as compared with the conventional CAV method, there is obtained an about 50% increase in capacity.
In the former method, however, the linear velocity of the disk is increased toward the outer periphery of the disk and this leads to a problem that the transfer speed of reproduced data is varied by the reproducing position of the disk, and the usability of the device as an information recording/reproducing apparatus is poor. Also, a reproducing signal processing system must accomodate the transfer speed of the outermost peripheral data, and if such a signal processing system does this, it can waste the inner peripheral portion of the disk.
Also, in the latter method, the transfer speed of reproduced data is constant in the inner and outer peripheries of the disk, but when the seeking of a recording/reproducing head is performed beyond a zone, a long time is taken until the number of revolutions of a spindle motor for rotating the disk becomes equal to the number of revolutions of the corresponding zone, and this has led to a problem that the seeking time becomes long.